Experimental validation for the diffraction effect in the ultrasonic field of piston transducers and its influence on absorption and dispersion measurements

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2001-03, Vol.48 (2), p.547-559
• Main Authors: Temsamani, A.B., Vandenplas, S., Lumori, M.L.D., van Biesen, L.
• Format: Article
• Language: English
• Subjects: Acoustic beams; Acoustic propagation; Acoustical measurements and instrumentation; Acoustics; Attenuation; Beams (radiation); Cross-disciplinary physics: materials science; rheology; Diffraction; Dispersion; Dispersions; Elasticity; Exact sciences and technology; Frequency estimation; Fundamental areas of phenomenology (including applications); Materials science; Materials testing; Mathematical models; Maximum likelihood estimation; Nondestructive testing: ultrasonic testing, photoacoustic testing; Physics; Pistons; Propagation; Studies; Transducers; Ultrasonic variables measurement; Viscoelastic materials; Viscosity
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/58.911738

The aim of this work was to study the diffraction effects in the ultrasonic field of piston source transducers and their importance for accurate measurements of attenuation and dispersion in viscoelastic materials. In laboratory measurements, the diffraction phenomena are mainly due to the beam spread of the ultrasonic wave propagating in viscoelastic materials. This effect is essentially related to the estimated attenuation and dispersion in the material. In this work, a frequency domain system identification approach, using the maximum likelihood estimator (MLE), was applied to the measured data in order to determine a function for correcting the diffraction losses in both normal and oblique incidences for a large frequency band (300 kHz to 3 MHz). The effective radius of the used transmitter was determined by the inverse problem when ultrasonic beam propagation was investigated in a water medium. Using the estimated radius, the propagation through viscoelastic materials was established, and the acoustic parameters of these materials were estimated. Attention was paid to the determination of the attenuation and dispersion in the materials. These quantities were compared to those obtained without diffraction correction in order to see the influence of introducing the diffraction correction into the propagation model.